1. Field of the Invention
The present invention is directed in general to field of information processing. In one aspect, the present invention relates to a multi-band wireless communication device, system and methodology.
2. Description of the Related Art
With the proliferation of new wireless communication standards and/or services which use different communication frequency channels or bands, wireless communication devices and/or network operators must increasingly be capable of providing services on multiple bands. The need of support multiple transmission/reception channels is also driven by spectrum scarcity when network operators providing services on one particular band are required to provide service on a separate band to accommodate its customers. For example, there are many different frequency bands used for mobile wireless applications, including but not limited to the Universal Mobile Telecommunications System (UMTS) frequency bands or frequency ranges designated for the mobile phone operation, such as the UMTS International Mobile Telecommunications (IMT) band operating in the 1.920-2.170 gigahertz (GHz) frequency range, the 3GPP Wideband Code Division Multiple Access (WCDMA) bands, the Personal Communications Services (PCS) band operating in the 1.850-1.990 GHz frequency range, the Digital Communications Services (DCS) band operating in the 1.710-1.880 GHz frequency range, the “900 band” operating in the 880-960 megahertz (MHz) frequency range, the “800 band” operating in the 824-894 MHz frequency range, etc., where each listed frequency band includes both transmit and receive frequencies. Thus, service in a given region could be provided on a GSM system in a 900 MHz frequency band and on a DCS system at an 1800 MHz frequency band, or even a third system, such as a PCS system in a 1900 frequency band. Similarly, service in another region could include an AMPS system in an 800 MHz frequency band and a PCS system in a 1900 frequency band. In this environment, a single network operator may not provide service in a plurality of systems in a given region. In similar fashion, a user of a wireless communication device may require the ability to roam across other systems in the event the user's device is unable to obtain service on one of the systems to which the user subscribes. Thus, mobile phone manufactures often need to design phones that are operable in multiple frequency bands for use by one or more different mobile phone service providers. Similar needs exist for other wireless applications.
While wireless communication devices, such as cellular radio telephones, have been developed which can communicate over a plurality of frequency bands, such devices typically use a transmitter subsystem which includes a dedicated transformer/balun and variable gain amplifier (VGA) for each frequency band. The conventional approach is illustrated in FIG. 1 which depicts a simplified schematic illustration of a conventional transmitter architecture for using as many baluns and VGAs as there are frequency bands. As depicted, a first output 1 from a mixer core (not shown) is fed into a first variable gain amplifier 4 which provides a differential output having a first fixed gain to the first transformer/balun 7 which converts the differential outputs to a single-ended output that is amplified by the first power amplifier 10 into a first transmission signal 13 on a first frequency band. In similar fashion, a second output 2 from a mixer core is fed into a second variable gain amplifier 5 which provides a differential output having a fixed gain to the second transformer/balun 8 which converts the differential outputs to a single-ended output that is amplified by the second power amplifier 11 into a second transmission signal 14 on a second frequency band, and a third output 3 from a mixer core is fed into a third variable gain amplifier 6 which provides a differential output having a fixed gain to the third transformer/balun 9 which converts the differential outputs to a single-ended output that is amplified by the third power amplifier 12 into a third transmission signal 15 on a third frequency band. As can be seen from this example, the inclusion of a dedicated balun and VGA for each band increases the overall device size, cost and power consumption. For example, with a cellular phone covering multiple 2G and 3G bands, twenty percent of the transceiver die area is used for the dedicated baluns and VGAs. Overall design complexity is also increased when using dedicated baluns and VGAs since, with multiple RF blocks or chains, the die routing is more complex, the drive capability must be increased, and the design cycle time is increased.
Accordingly, an improved transmitter design and methodology is needed to overcome the problems in the art, such as outlined above. Further limitations and disadvantages of conventional approaches will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow.